An ozone gas, which has strong oxidative power and has no remaining toxicity after being decomposed, has been widely used for deodorants, bactericides, oxidation treatment of semiconductors, and so forth.
An ozone gas can be generated by electric discharge in an atmosphere containing an oxygen gas, for example. In the case of generating an ozone gas in this manner, it is known that addition of a trace amount of a nitrogen gas to an oxygen gas as a raw material increases the concentration of the ozone gas and enhances stability with time. In such a case of adding a trace amount of a nitrogen gas to an oxygen gas as a raw material, the added nitrogen gas partially becomes a nitrogen oxide. This nitrogen oxide can cause corrosion of pipes serving as channels for gases.
As a technique for removing a nitrogen oxide contained in an ozone gas, a method for removing a nitrogen oxide by introducing an ozone gas in which the nitrogen oxide is mixed into a removing cylinder filled with silica gel is proposed. (see, for example, Japanese Patent Application Laid-Open No. 2011-121805: Patent Document 1).